Civil servants sometimes have to delay or even block ministers’ plans and it
is their job to do so, the Cabinet Secretary has said.

Sir Jeremy Heywood accepted that some ministers are “frustrated” by the way officials have responded to their instructions, but insisted that civil servants were right to act as they did.

He also rejected calls from Conservatives for more politically-appointed special advisers to be given posts in Downing Street.

“On occasions, civil servants have been responsible for insisting on due process and slowing things down and make things go through a proper decision-making process -- that’s our job,” Sir Jeremy told a Commons committee.

“Part of our role is to give advice, as to whether something will work, whether something is contrary to the law. Occasionally that will come across as tying to slow things down or stop things happening – that is part of our job. I think it is absolutely right that the Civil Service plays that role.”

Sir Jeremy insisted that officials do not deliberately try to frustrate ministers, and always try to obey instructions within the law.

“If the general policy of the government is to deregulate, we will turn the tanker around and start applying ourselves to that agenda,” he said.

“Unfortunately, one or two of these things are laid down in statue or are quite difficult for the Civil Servant to do very much about.”

Several Conservative ministers and Government advisers have complained privately about the behaviour of civil servants, accusing officials of being unduly obstructive.

David Cameron this week said that forthcoming reforms of the civil service will lead to “leaner, swifter" government and help ministers implement their promised reforms.

“It is true that some ministers and advisers have clearly been more frustrated,” Sir Jeremy said, accepting that officials have to win the trust of ministers.

“We have to prove by our day-to-day competence that we are supporting the elected government of the day.”

Steve Hilton, the Prime Minister's senior adviser, has suggested that civil service reform could mean as many as 90 per cent of civil servants lose their jobs.

It leaves civil servants “frustrated and angry when that is put in the newspapers as an authorised briefing,” Sir Jeremy said.

Mr Hilton's idea, is "something that has no authority at all," he added. “Wherever it has come from it, it does not reflect the position of the Government”

Asked about Mr Hilton, Sir Jeremy said: "The way Steve operates is to challenge. Steve is a very challenging person."

Sir Jeremy also suggested he was opposed to suggestions from some Conservatives that No 10 needs more Conservative special advisers to push the party's agenda.

"I’m comfortable with the current levels. I wouldn’t want to see them dramatically increasing," Sir Jeremy said. "I think government is working perfectly well with the number of special advisers it has got."

Some ministers believe that the No 10 policy unit, currently staffed by civil servants, should be filled with politically-partisan special advisers.

Mr Heywood said that was not possible, because Mr Cameron had taken the decision to have a single policy unit in No 10 serving both Conservative and Lib Dem ministers.

"If you take the decision, it is quite difficult to see how it can be staffed with special advisers. You are driven to having a more technocratic group of people."